Within recent years, vinylidene chloride copolymers which rely upon copolymerizable surfactant comonomer systems have been reported (e.g., see U.S. Pat. Nos. 3,850,726; 3,714,106 and 3,736,303 by Smith et al.; 3,449,302 by Nachbur et al.; 3,617,368 by Gibbs; 3,843,581 by Gibbs et al.; 3,946,139 by Blyle et al., etc.). Particularly noteworthy are U.S. Pat. Nos. 3,850,726 and 3,714,106 by Smith et al. which enable the art to effectively coat unprimed polyolefin films with a high-solids, low viscosity vinylidene chloride copolymer latex. The Smith et al. latices have excellent film wetting and adhesion properties and provide coatings of exceptional heat-seal and dynamic peel strength properties.
U.S. Pat. No. 3,839,393 by Steckler discloses a method for preparing salts of sulfato-alkane acrylate and methacrylate. These salts are reportedly useful in preparing emulsion copolymers with certain comonomers such as acrylonitrile, vinyl chloride, styrene, n-butyl acrylate and methacrylic acid. Steckler discloses the reddish-purple, viscous liquids obtained by reacting sulfamic acid and hydroxyalkane acrylates or methacrylates are suitable for polymerization reactions and various industrial applications such as protective coatings, textile binders, paper coatings, etc.
The inventor sought to develop a unique vinylidene chloride copolymer latex system which possessed greater versatility in coating applications than existing internally emulsified copolymer latices. He desired a vinylidene chloride copolymer system which could be utilized to coat unprimed polyolefin without relying upon sulfoalkyl ester of alpha, beta-ethylenically unsaturated carboxylic acid comonomers. The inventor contemplated a stable vinylidene chloride copolymer latex system which possessed uniform and excellent wetting and adhesion attributes to impervious plastic substrates and especially suited for use at a high-solids, low viscosity levels in conventional high-speed film coating and heat-sealing operations. It was also desired to achieve vinylidene chloride copolymer coatings of excellent heat-sealing and dynamic peel strength properties. A more versatile vinylidene chloride copolymer latex system capable of providing superior oxygen-barrier and block-resistant coatings at a reduced level of copolymized vinylidene chloride comonomer was also sought by the inventor.